Lock cylinder

Abstract: A lock cylinder comprises a cylinder body wherein a cylinder plug (1) comprising a clot (2) for the key (18) of the lock is rotatably arranged. The profile of the key slot and therefore also of the key is determined by profile forming elements in the form of rotation bodies (6,7) which are inserted in bores (4,5) extending through the cylinder plug (1) parallel to and adjacent to the middle plane (10) of the key slot (2). The profile elements (6,7) may be made of hardenable steel, for instance by turning, and may comprise a number of portions of different diameter so that the total number of key profiles obtainable becomes high while permitting the key profile to be made very thin and correspondingly difficult to copy.

Description: The present invention relates to a lock cylinder comprising a cylinder body wherein a cylinder plug is rotatably arranged, said cylinder plug being provided with bores for tumbler pins and comprising a slot for the key belonging to the lock cylinder, said key slot having at least one portion provided with a cross-sectional profile which is adapted to the profile of the key, said cross-sectional profile at least partly being formed by two profile elements constituted by rotation bodies arranged axially immovably in bores in the cylinder plug substantially on either side of the middle plane of the key slot, the profile elements having varying diameter and being arranged substantially parallel to and near the middle plane of the key slot. It is known to make the cylinder plug for different key profiles as an element or a major part of a lock system. Also for other reasons, i.a. due to safety considerations, it is desirable to make many different profiles. The larger the number of different profiles, the higher the number of key variations that can be made. The most common method for making key hole profiles today is to broach the channel with a toothed steel broach in a machine made especially for this purpose. The broach is often about one meter long and is driven through the cylinder plug while the teeth on the broach are cutting chips from the cylinder plug. This method has many drawbacks and deficiencies but is nevertheless the method most widely used today. Among the drawbacks are that the machine and broach are relatively expensive equipment. The long broaches are also cumbersome to replace in the machine and there is therefore a limit to the practicable number of different profiles (broaches) available. Another deficiency is that the key slot must have a certain minimum cross-section at all points determined by the strength of the teeth of the broach. The profile of the key slot is also in other respects shaped in accordance with the limits of the broach. For instance, the pitch angle of the grooves of the profile must be such that abrupt cross-sectional changes are avoided. If the profile has abrupt cross-sectional changes, the teeth of the broach will easily break. In other words, the shape is governed by the tools and method rather than the desired function. There is known a number of suggestions that aim at avoiding the above drawbacks by placing exchangeable profile determining elements at the front of the cylinder plug. However, none of these suggestions have found industrial applicability to any notable extent. Thus, from US patent No. 4.231.242 there is known a lock cylinder where the key profile fitting the key slot is determined by two studs installed with force fits in bores extending transversally of the key slot, said studs extending some distance into the key slot from either side. The installation of these studs is cumbersome, e.g. because it requires special measures for determining exactly how far into the key slot the studs are to extend and because those parts of the studs that following installation are left on the outside of the cylinder plug must be ground away. The studs cannot later be moved if one later should wish to change the profile of the key, but instead one has to install a further stud in a reserve bore. The possibilities of a later change to other key profiles are therefore quite limited and the same holds for the total number of possible key profile varieties. A further drawback is that the access to the key slot for common picking tools is not particularly difficult. From Swedish patent No. 469565 a cylinder lock is known where the tumbler pins acted upon by the key lie to the side of the middle plane of the key slot and are provided with a circular flange cooperating with a slot in the side face of the key, said slot acting to lift the tumbler pins to an extent depending upon the combination of the lock. These tumbler pins cannot be used to change the profile of the key and they restrict the cross-section of the key slot to such a small degree that picking tools have fairly easy access. From AT patent 392506 a lock cylinder is known of the type described in the introductory paragraph of this specification, namely a lock cylinder according to the preamble of claim 1. In this cylinder, the key slot is for the major part made in the usual way by broaching. In addition, the key slot is partly modified by two profile elements being rotation bodies and having a pointed contour extending into the broached key slot and necessitating corresponding grooves in the key to accommodate the profile elements. Since the profile elements are located about equidistant from the ends of the cylinder plug, the additional grooves in the key extend only for about half the length of the key bit. The purpose of the present invention is to provide a lock cylinder of the introductory type which can be manufactured in an effective and cost efficient manner and which makes it easy to change the profile of the key while making the access for picking tools very difficult. This is obtained according to the invention in that the bores for the profile elements extend through the cylinder plug, that the profile elements have a length close to the diameter of the cylinder plug, that the profile elements comprise a plurality of portions having larger diameter than the adjacent portion or portions of the profile elements, and that the profile of the key slot is defined substantially by the profile elements only. Since the profile elements easily are made in a great number of varieties and with quite abrupt cross-sectional changes, the number of possible key varieties becomes very high, and the key opening between the profile elements may in one or more portions be made so narrow and irregular that picking tools cannot pass. Furthermore, the key profile of the lock can very simply be changed by exchanging the profile elements or letting them switch place. Besides, keys can be made that are very difficult to copy for unauthorized persons, this also being an important improvement as compared to the keys used today. Further advantageous features of a lock cylinder according to the invention are recited in the dependent claims 2-8. The invention also relates to a key fitting the lock cylinder according to the invention. This key comprises a key bit for the introduction into the key slot formed between the profile elements in the cylinder plug, and the key bit having a narrow web portion which interconnects a middle and a lower flange portion. In order to obtain a key that is simple to manufacture and permits a key slot that restricts the entry of picking tools, the web portion of the key according to the invention has a height which is between 1/3 and 1/4 of the total height of the key bit and a thickness which is between 1/6 and 1/10, preferably about 1/8, of the largest thickness of the largest of said flange portions. For better understanding of the invention it shall be described more closely with reference to the exemplifying embodiments shown in the appended drawings, wherein: Figure 1 shows a cylinder plug according to an embodiment of the invention viewed from above, without tumbler pins and profile elements, Figure 2 is a section along the line II-II in Figure 1, with the profile elements in place and a key introduced into the plug, Figure 3 shows an alternative embodiment of the cylinder plug, Figures 4-7 show various key profiles, and Figure 8 shows the key profile of Figure 7 with the two profile elements forming the corresponding key slot. In the various figures like or corresponding parts are given the same reference numerals. The cylinder plug 1 shown in Figure 1 is provided with a longitudinal key slot 2 having a generally rectangular cross-section. The plug has bores 3 for the usual tumbler pins and bores 4 and 5 for the key slot profile forming elements of the plug. Figure 2 shows the shape of the profile forming elements 6,7. They are in the form of rotation bodies having varying diameter. They are preferably made by turning of a hardenable steel. It will be understood that other methods of manufacture may be used, for instance hard metal sintering. The bores 4,5 for the profile elements 6,7 are arranged with their axes 8,9 parallel to the middle plane 10 of the key slot and are generally equidistant from the middle plane. As may be seen from Figure 1, however, the bores 4,5 are arranged offset with respect to each other in a longitudinal direction of the plug. This contributes i.a. to maintaining the strength of the plug in this area and facilitates placing the bores adjacent to the middle plane of the key slot without the bores coming into direct contact with each other. At one end the profile elements 6,7 have a straight cylindrical portion 11 and 12, respectively, which fits with little clearance in the respective bore 4,5. This cylindrical portion provides sufficient lateral support for the profile element but for reasons of mechanical strength, the profile elements should preferably have at least one further portion with the full diameter closer to the other end, for instance like the portions 13 and 14 shown in Figure 2. The bores 4,5 for the profile elements are through-going and the profile elements have rounded end surfaces 15,16, the radius of curvature of which is less than the radius of the cylinder plug 1. The end surfaces 15,16 can therefore generally contact and abut against the inner periphery (not shown) of the cylinder body so that further axial restraint of the profile elements becomes unnecessary. The through-going bores will make it easy to replace the profile elements after the cylinder plug first having been pulled somewhat out of the cylinder body. At their lower ends the profile elements have a portion 17 of reduced diameter which, together with the rounded end surface 16, permit a portion of full width at the lower part of the key 18. This may be of importance for the strength of the key when the remaining part of the profile is narrow, as in the example shown in figure 2. It will be apparent that the diameter of the bores 4,5 for the profile elements is larger than the diameter of the bores 3 for the tumbler pins. The diameter of the former bores may be about twice the thickness of the key 18. The profile elements may thus be shaped to take advantage of the full thickness of the key without their narrowest portions becoming too weak. As is easily seen from Figure 1, the profile elements can be manufactured with a multitude of profiles so that a large variety of keys may be used. If, for example, ten different profiles for each of the two profile elements 6,7 are available, 10x10 = 100 key profiles may be obtained. In Figure 3 an alternative embodiment of the cylinder plug 1 is shown. Here, the bores 4,5 for the profile elements are placed adjacent to each other along the middle plane 10 of the key slot, and two further bores for a second pair of profile elements are arranged inwardly of the first bores with a tumbler pin bore 3 in between. By means of this construction the access to the innermost tumbler pins with a picking tool is very effectively prevented. The two pairs of profile elements may be identical, or they may be different and together define the key profile. In the latter case the key profile can be given a very intricate form without the profile elements becoming correspondingly difficult to manufacture. Figures 4-7 illustrate four different embodiments of the profile of the key bit 19 of the key 18 according to the invention. The key bit comprises a lower flange 20 and a middle flange 21 which are interconnected by a narrow web portion 22. The web portion has a height h which is between 1/3 and 1/4 of the total height H of the key bit. The narrow web portion 22 has a thickness t which is between 1/6 and 1/10 of the largest thickness T of the flanges 20,21, preferably about 1/8 of this thickness. It will be apparent that the narrow web portion 22 is intersected by the middle plane of the key bit once in Figure 6, twice in Figures 4 and 5 and four times in Figure 7. In addition to the part of the key slot in the cylinder plug 1 corresponding to the web portion of the key bit being very narrow, the irregular form of this part of the slot will make it practically impossible to introduce a picking tool into the cylinder plug. Particularly the zigzag form in Figure 7 is especially effective in this respect. Even though the narrow web portion 22 is very thin and has a considerable height, the key nevertheless becomes strong enough because the web, together with the two flanges 20,21, forms an approximate I-beam profile. Figure 8 shows the shape of the two profile elements 6,7 forming the key slot for a key having a profile as shown in Figure 7. It will be understood that the invention is not restricted to the exemplifying embodiments shown but may be varied in a number of ways within the scope of the appendant claims.

Claims: A lock cylinder comprising a cylinder body wherein a cylinder plug (1) is rotatably arranged, said cylinder plug being provided with bores (3) for tumbler pins and comprising a slot (2) for the key (18) belonging to the lock cylinder, said key slot (2) having at least one portion provided with a cross-sectional profile which is adapted to the profile of the key, said cross-sectional profile at least partly being formed by two profile elements (6,7) constituted by rotation bodies arranged axially immovably in bores (4,5) in the cylinder plug (1) substantially on either side of the middle plane (10) of the key slot, the profile elements (6,7) having varying diameter and being arranged substantially parallel to and near the middle plane (10) of the key slot (2), characterized in that the bores (4,5) for the profile elements (6,7) extend through the cylinder plug (1), that the profile elements (6,7) have a length close to the diameter of the cylinder plug (1), that the profile elements (6,7) comprise a plurality of portions having larger diameter than the adjacent portion or portions of the profile elements, and that the profile of the key slot (2) is defined substantially by the profile elements (6,7) only. A lock cylinder according to claim 1, characterized in that the bores (4,5) for the profile elements (6,7) are offset with respect to each other in the longitudinal direction of the cylinder plug (1). A lock cylinder according to claim 1 or 2, characterized in that two further bores (4',5') for a second pair of profile elements are arranged inwardly of said bores (4,5) for the profile elements. A lock cylinder according to claims 1, 2 or 3, characterized in that at least some of said portions of the profile elements (6,7) having larger diameter have a right-angled contour. A lock cylinder according to any one of the preceding claims, characterized in that the profile elements (6,7) have rounded end surfaces (15,16) which have a radius of curvature less than the radius of the cylinder plug (1) and which generally abut the inner periphery of the cylinder body. A lock cylinder according to any one of the preceding claims, characterized in that the profile elements (6,7) have, respectively, at least two portions (11,13;12,14) with close to the same diameter as the bores (4,5) for the profile elements (6,7) in the cylinder plug (1). A lock cylinder according to claim 6, characterized in that one of said portions (11;12) is located at one end of the respective profile element (6,7) while the other portion (13;14) is located closer to the other end of the profile element. A lock cylinder according to any one of the preceding claims, characterized in that the profile elements (6,7) are made of hardened steel. A key for use in a lock cylinder according to one of claims 1-8, comprising a key bit (19) for the introduction into the key slot formed between the profile elements (6,7) in the cylinder plug (1), the key bit (19) having a narrow web portion (22) which interconnects a middle and a lower flange portion (21,20), whereby said web portion (22) has a height (h) which is between 1/3 and 1/4 of the total height (H) of the key bit (19) and a thickness (t) which is between 1/6 and 1/10, preferably about 1/8, of the largest thickness (T) of the largest of said flange portions (20,21). A key according to claim 9, characterized in that said web portion (22) is intersected by the middle plane (23) of the key bit (19) in at least one, preferably in a plurality of places.

Inventors: SORNES TOR, SORNES, TOR
Applicants: TRIOVING AS
Application year: 1994
Main classification: E05B27
IPC codes: E05B19, E05B27, E05B15